Many product applications require glass powders that have one or more of the following properties: high purity, controlled chemistry, spherical morphology, small average size, narrow size distribution, and little or no agglomeration. Glass powder applications requiring such characteristics include, but are not limited to, thick film pastes used for fabricating electronic devices. Thick film pastes are mixture of the powders in an organic vehicle, wherein the organic vehicle is removed after application of the paste to a substrate by firing the composition at elevated temperatures.
Most glass powders are produced by forming a melt of the desired glass composition, quenching the molten glass and milling the resulting glass to reduce the particle size. A glass lacks the long range regular periodic arrangement of atoms characteristic of materials considered crystalline to one skilled in the art. When glass is analyzed by X-ray diffraction the resulting data lacks the distinct peaks seen in materials considered crystalline, yet instead shows a broad signal over wider range of 2θ angles; this range being typical greater than 5 to 20° 2θ. The milling process results in glass powders having an irregular morphology and high surface area which can be undesirable in precision applications.
Aerosol decomposition of an atomized liquid spray of precursor solution is a useful method for producing glass-crystalline particles and spherical glass-crystalline particles with high purity, controlled chemistry, small average size, narrow size distribution, and little or no agglomeration. In such a process, a precursor solution containing the elements desired in the final glass is atomized to produce an aerosol. The aerosol particles are then transported through a reaction tube where the solvent is removed and the aerosol particles are heated to a temperature sufficiently high to convert the precursor compounds to product glass particles. At these high temperatures a suitable material of construction reactor tube needs to be used.
There is a need for glasses with improved properties including making particles with a spherical shape and making glass-containing particles. There is need for improved aerosol methods useful for the production of glass powders. In addition, there is a need for improved devices useful in the methods of making glasses by aerosol methods.